Gummed strapping tape



April 6, 1954 w. H. PAHI. ET AL GUMMED STRAPPING TAPE Filed Aug. 17, 195o Patented Apr. 6, 1954 GUMMED STRAPPING TAPE Walter H. Pahl, Western Springs, and Keith H.

Williams, Aurora, St. Paul, Minn.,

Ill., and Hubert J. Tierney, assignors, by inesne assignments, to'-Minnesota Mining' &. Manufacturing Company, Delaware St. Paul, Minn., a corporation of Application August 17, 1950, Serial No. 180,045

2 Claims. l (Cl. 15d-53.5)

This' invention relates tof lineally reinforced gummed papertape, sometimes referred to as strapping tape.

Prior constructions of this' type of' tape have included the addition to the normal combination of,A backing and adhesive, of a plurality of elongate members or elements (such as threads, strands or fibers) that have a high tensile strength, such elements being in or on the backing', in or'y onthe adhesive', or between the adhesive and the backing.

Such prior" constructions however,.have been unsatisfactoryfin' many Ways.

An objective therefore is to provide a lineaily reinforcedgummed paper tape ofimproved construction and performance, and'having a tensile strength of at least 100 pounds per inch width.

The invention provides a tape having a backing and a' coating ofa normally nonetacky adhesive'on one surface of the backing, the said backing beingv a` laminated structure'comprising two sheets of paper adhered' to eachother by a layer' of a rubber-resin type pressure-sensitive adhesive which is waterproof and is stably and normally tacky, anda non-woven layer of continuous hair-like organo-synthetic textile laments fully embedded'within the adhesiveV layer and unified therewith, they filaments beingaligned lineally in respect to the tape. The iilaments may be single or in yarns.

' An illustrative embodiment is described below and illustrated in the accompanying drawings in which:

Figure l is a schematic diagram showing in perspective a length of the tape;

Figure 2 shows a method and apparatus for its making; and

Figure 3 shows a carton boundor strapped with the tape.

A sheet I of 60 `pound kraft paper (kraft paper havinga ream` weight of 60 pounds per 300D square feet) is led from a supply roll 2 thereof through a coating apparatus 3 Wherexa layer of a stably and normallyv tacky adhesive 4 ofthe rubbeiresin type that is-oonnnonly used as the adhesive layer in pressure-sensitive adhesive tapes, applied. Thereafter it passes through a drying oven E and thence between two laminating rollers G and i Where a layer oi continuous rayon lament yarns is applied to the adhesive side.

The yarns are drawn from a warp beam S to combs lil and thence to the laminating rollers Gland i Where, in going through the nip, they are pressed into the suriace'of the soft, dried,

coating of adhesive' 4 to form a lineally aligned mono-layer'of continuous yarns 8 that are held in place by the tackiness of the adhesive.

The laminated sheeting proceeds horizontally, yarn side up, to a second coating apparatus it which applies a layer of adhesive I2 to the yarn side of the sheeting.

The layers li and I2 of adhesive commingle so that. they form a single adhesive layer I3 having a layer of filament yarns embedded therein.

After next passing through a second drying oven I4, the sheeting is then directed between a second set of laminating rolls i 5 and is Where a pregumined sheet Il' of 20 pound kraft paper, its exposed surfacey having been previously coated with a layer IB of high strength glue, is applied to the adhesive side of the laminated sheeting.

The pregummed paper sheet i'i is led from asupply roll I9 thereof and its uncoated side is pressed into contact with the pressure-sensitive adhesive layer i3, thus completing the laminated structure shown in-Figure 1. The nished product is wound up in a storage roll 20.

The adhesive layer I3 being pressure-sensitive, the lamination at the rolls l5 and I@ may take place' atl room temperature. This avoids any deleterious effects that might come from the application of heat.

There are numerous alternatives.

For example, the paper i'i may be uncoated when it is laminated to the adhesive layer ifi, ifN desired. In such case, the glue layer I8 may beA applied after the laminated sheeting has passed from the roll I5 and is on its way to the storage-roll 2.0.

Other high strength normally non-tacky adhesives; such as water-activatable or heat-activatable adhesives, may be used in place of the glue I8.

The weights ofthe papers .may vary.

A' layer of 100 yarns per inch of 300 denier 60 ilainent yarn rayon, has'produced tape having a tensile strength of more than 150 pounds per inch Width.

The'organo-synthetic laments may be of materials other than rayon and of other sizes and count;

The adhesive is one of the various rubber-resin type pressure-sensitive adhesives of the type well known in the art as suitable for the adhesive coating on pressure-sensitive adhesive tapes; and such adhesives are the ones meant herein by the expression rubber-resin type pressureesensitive adhesive. These adhesives are Water-insoluble and aggressively tacky. They have a rubbery base of natural or synthetic rubber which provides cohesion (internal strength) and elasticity (a retractive force when stretched and retraction when released after stretching) and this rubber base is modied by blending with a compatible tackier resin (such as rosin or ester gun) which serves to increase adhesion (tackiness) and decrease cohesion, with an attendant increase of stretchiness (elongation under low stresses) and decrease of elasticity.

These rubber-resin tape adhesives have a proper four-fold balance of adhesion, cohesion, stretchiness and elasticity. They are termed eucohesive by which it is meant that they are more cohesive than adhesive.

Certain synthetic polymers are inherently tacky and eucohesive and possess the above-mentioned four-fold balance of properties, and can be used as pressure-sensitive tape adhesives, thus being equivalents of the rubber-resin adhesives and hence they may be regarded as being of the rubber-resin type. An example is a 75:25 copolymer of 2-ethyl-butyl-acrylate and ethyl acrylate.

The lineally aligned, continuous, lhair-like organo-synthetic textile laments and the surrounding rubber-resin type pressure-sensitive adhesive provide a reinforced adhesive layer I3 of novel construction having novel properties. These mono-fiber filaments are individually encased and permanently bonded by the aggressively tacky adhesive to which they are individually united, even when present in twisted yarns.

This adhesive has elasticity and it is quite stretchy. This can be clearly demonstrated by separating the adhesive layer I3 from the other backing layers, as by soaking a length of the tape in water and then peeling the paper layers I and Vl from either side of the filament-containing adhesive layer I3. The said separated adhesive layer I3 can be pulled crosswise between the iingers to two or three times its initial width without rupturing. Because of this property of the adhesive, together with the fact that it is permanently bonded to the filaments by virtue of its aggressive tackiness, the filaments are capable of movement relative to each other and relative to the backing without rupture of the bond between the adhesive and the laments, without rupture of the bond between the adhesive and the paper layers, and without internal rupture of the adhesive. Not only does this make for a high degree of lengthwise and crosswise flexibility 'out it permits of elongation of the yarns or free lilaments when the tape is stressed, and of their retraction when the stress is decreased or removed. so as fully to capitalize upon their stretchability and resiliency.

It may be noted that these organo-synthetic textile filaments and yarns posses a substantial degree of stretchability and resiliency, unlike glass filaments and yarns, and the present tape construction fully utilizes this property. A very important feature is that this structure allows a relative shifting of the mono-fiber laments so that when the tape is subjected to non-uniform stresses the load `will be more eiectively distributed as between the various filaments, thereby more nearly equalizing the strains on the yarns or free laments and, increasing the effective resistance of the tape to breaking. This is of particular value in obtaining ay maximum resistance to shock stresses such as are produced, for example, when a bundle of steel rods is dropped on the floor and .i ments do not adhere to rubber.

the adhesive tape straps are suddenly subjected to strong bursting forces which are non-uniform across the width and along the length of the tape.

This is in direct contrast to the aforementioned reinforced gummed paper ta-pes heretofore known to us, wherein the reinforcing strands or bers are held by an adhesive that loses its tack after application, such for example as glue, or by a tacky adhesive that has no stretch. If in such a tape, the stress and strain of use causes sufcent relative movement between a strand and the adhesive to break the strand loose from the adhesive, the adhesion between the two is never restored and the tape becomes weakened at that point. In the tape of the present invention, however, the adhesion between the filaments and the adhesive is never broken.

In the new tape of the present invention, a series of continuous mono-liber filaments are clamped, as it were, along their full lengths by permanently adherent adhesive, and this adhesive is highly cohesive. The effect of this is to increase the effective tensile strength of the embedded yarns or free laments, their combined tensile strength being greater than the aggregate strength of an equal number of uncoated yarns or free filaments.

The adhesive Vfurther serves to absorb and damp shock forces because of its yieldable and resilient nature, thereby increasing the effective strength of the yarns or free laments in respect to shock stresses. It should be noted that the adhesive has a low tensile strength per se, a layer of non-reinforced adhesive being quite easily pulled out between the fingers to the breaking point. Hence it is evident that a combination or co-active effect is involved.

A further co-active effect is involved in respect to the backing. The paper sheets I and I'I are clamped to the layer of yarns or free filaments by the tacky, stretchable, adhesive. When the tape is elongated under a lengthwise pull it is found that the paper can elongate to a greater extent before rupture than otherwise is the case.

Moreover, if a paper is used which will break before the i'ilaments break, the continuity of the tape and its lengthwise strength is retained since the filaments are the load-carrying elements.

The organo-synthetic mono-liber textile fila- A continuous man-made filament which is encased by rubber can be pulled out, being a smooth-surfaced cylinder held only by friction. This is in contrast to natural fibers. A yarn formed of twisted continuous organo-synthetic filaments has only a limited degree of anchorage to rubber in which encased. In the present gummed strapping tape the organo-synthetic yarns and filaments require no special treatment in order to be firmly bonded, owing to the fact that the rubber-resin type adhesive, unlike rubber per se, wets the fiber surfaces and has a strong specific adhesion to them. And as above pointed out, this adhesive bond is not broken by movement of the filaments inasmuch as the adhesive is very stretchy. The

wetting action of the adhesive also facilitates its penetration between the filaments so as thoroughly to contact their surfaces.

The organo-synthetic textile filaments are sensitive to the presence of water and are permeable thereto in varying degrees depending upon the particular kind. Viscose and other regenerated cellulose rayon fibers are especially' moisture-permeable. These fibers are weaker when moist than when in a normal dry state.

but when dried to an extreme they become brittle and weak. Cellulose bers are not dimensionally stable and they shrink or expand as the moisture content varies. In the present construction, the yarns and laments all run lengthwise of the tape and are sheathed by a waterproof, moisture-proof, hydrophobic adhesive. The laments are exposed to the air only at the ends of the tape, where it has been cut. Thus the filaments preserve their initial state which they have when incorporated into the adhesive and this initial state can be controlled for optimum properties. Gain or loss of moisture can take place at only a very slow rate since the hair-like filaments are extremely long relative to cross-sectional area and are exposed to the atmosphere only at the ends of the tape, and in a roll of tape the laments are many yards long and the inner end of the tape is covered.

Since the yarns or filaments are aligned and run straight they are in a condition of maximum strength, unlike the undulating threads of Woven cloth which cross over each other and bear into each other when a strong pullling force is applied. This also makes for greater lengthwise and crosswise flexibility, and there are no fiber ends exposed at the side edges of the tape. The yarns can be closer together than in woven cloth, and untwisted filaments can be used. These factors all contribute to making possible extremely strong adhesive strapping tapes having maximum flexibility and suppleness and minimum thickness.

The present adhesive strapping tape also has novel structural properties in that the lengthwise tensile strength and crosswise tear strength are mainly due to the lineally aligned laments embedded within the pressure-sensitive adhesive (i. e. to the filament-reinforced pressure-sensitive adhesive layer I3), whereas the crosswise -tensile strength and lengthwise tear resistance are mainly due to the paper. The paper layers and the reinforced adhesive layer thus perform distinct functions in respect to strength properties. Crosswise tensile strength and lengthwise tear strength are of secondary importance for strapping purposes. The present construction avoids an unnecessary degree of `.crosswise tensile strength and lengthwise tear strength and thereby makes it possible to employ ordinary untreated paper for the backing.

Thus the particular tape structure of the present invention has a peculiar and useful combination of capacities and characteristics which are not possessed by the aforementioned varieties of reinforced gummed paper tape known to us.

As indicated by the name strapping tape," it nds particular utility when used to accomplish the work of a band or strap to bind or tie bundles, cartons or package.

Figure 3 illustrates such a use. When cardboard cartons are used to hold very heavy materials, metal bands are usually required to bind them. Such a non-adherent band must go around the entire carton in order to be fastened. Tapes made according to the present invention, however, have tensile strengths suicient to enable them to replace such metal bands; and being gummed, can be adhered to the carton so that the tape need not encircle the carton, as must the metal band, thus being the cheaper both in respect to initial cost and quantity used. Additionally, metal bands tend to weaken the carton by cutting it at the corners, whereas the tape of this invention not only avoids such cutting and weakening but serves actually to reinforce and to strengthen the carton.

We claim:

1. A gummed tape of the character described comprising a backing and a coating of a normally non-tacky adhesive on one surface of the backing, the said backing being a laminated structure comprising two sheets of paper adhered to each other by'a layer of a rubber-resin type pressure-sensitive adhesive which is Waterproof and is stably and normally tacky, and a nonwoven layer of continuous hair-like organo-synthetic textile filaments fully embedded within the adhesive layer and unified therewith, the filaments being aligned lineally in respect to the tape.

2. A tape according to claim 1 in which the filaments are rayon.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 1,167,466 Angier Jan. 11, 1916 1,446,094 Jackson Feb. 20, 1923 1,872,316 Meeker Aug. 16, 1932 2,089,405 Newkirk Aug. 10, 1937 2,444,830 Kellgren et al. July 6. 1948 FOREIGN PATENTS Number Country Date 128.707 Switzerland Nov. 16. 1928 

1. A GUMMED TAPE OF THE CHARACTER DESCRIBED COMPRISING A BACKING AND A COATING OF A NORMALLY NON-TRACKY ADHESIVE ON ONE SURFACE OF THE BACKING, THE SAID BACKING BEING A LAMINATED STRUCTURE COMPRISING TWO SHEETS OF PAPER ADHERED TO EACH OTHER BY A LAYER OF A RUBBER-RESIN TYPE PRESSURE-SENSITIVE ADHESIVE WHICH IS WATERPROOF AND IS STABLY AND NORMALLY TACKY, AND A NONWOVEN LAYER OF CONTINUOUSLY HAIR-LIKE ORGANO-SYNTHETIC TEXTILE FILAMENTS FULLY EMBEDDED WITHIN THE ADHESIVE LAYER AND UNIFIED THEREWITH, THE FILAMENTS BEING ALIGNED LINEALLY IN RESPECT TO THE TAPE. 